The present invention relates to a novel and useful antibody having a specific affinity for endothelin-3 and a precursor of endothelin-3, for example, big endothelin-3 and more particularly to an antibody useful for development of assays of endothelin-3 and a precursor of endothelin-3, for example, big endothelin-3 on the basis of antigen-antibody reactions or for diagnosis and treatment of diseases related to endothelin-3.
Endothelin-1 is a peptide which consists of 21 amino acid residues and was discovered in a culture supernatant of vascular endothelial cells, and has very strong vascular smooth muscle constrictor activity and vasopressor activity. From the analysis of cDNA of endothelin-1, it has also been deduced that big endothelin-1 (a precursor of endothelin-1) comprised of about 40 amino acid residues exists as an intermediate in the course of its biosynthesis. Until now, monoclonal antibodies to endothelin-1 and big endothelin-1 have been prepared and high sensitive enzyme immunoassays have been developed, whereby it has become possible to widely extend research toward the elucidation of the physiological role of endothelin-1 and the pathologic role thereof. The use of the monoclonal antibodies having neutralizing activity as specific antagonists has revealed that endothelin-1 is deeply related to ischemic diseases, and further detailed research has been advanced for the relation between the plasma endothelin-1 level and its pathologic role, using the above assays.
On the other hand, from the analysis of chromosomal DNA, the sequences of endothelin-1 and endothelin-2 have been newly discovered, and it has been revealed that the endothelins form a gene family. In particular, endothelin-3 differs from endothelin-1 and endothelin-2 in 6 residues (underlined) of 21 amino acid residues, as shown below, and it has been reported that endothelin-3 is considerably weaker in vascular smooth muscle constrictor and vasopressor activities than endothelin-1 and endothelin-2. Endothelin-1 (porcine or human, which was also referred to as endothelin-.alpha.): EQU Cys Ser Cys Ser Ser Leu Met Asp Lys Glu Cys Val Tyr Phe Cys His Leu Asp Ile Ile Trp
Endothelin-2 (human): EQU Cys Ser Cys Ser Ser Trp Leu Asp Lys Glu Cys Val Tyr Phe Cys His Leu Asp Ile Ile Trp
Endothelin-3 (rat or human.-, which was also referred as endothelin-.gamma.): EQU Cys Thr Cys Phe Thr Tyr Lys Asp Lys Glu Cys Val Tyr Tyr Cys His Leu Asp Ile Ile Trp
Further, the analysis of cDNA of endothelin-3 has revealed the structure of a precursor of endothelin-3 (Japanese Patent Unexamined Publication No. 1-253797/1989), and it has been suggested that endothelin-3 is synthesized from big endothelin-3 as a direct precursor, having the following sequence: ##STR1## (wherein X is Gly--OH, Gly--NH2, Gly--Lys--OH or Gly--Lys--Arg--OH.)
The structure of an additional precursor of endothelin-3 has been deduced, and is a polypeptide having the following amino acid sequence: ##STR2##
Thus, the results of the studies of their structure and pharmacological activity strongly suggest that endothelin-3 forms a receptor system different from those of endothelin-1 and endothelin-2, and a deep interest is taken in the physiological role of endothelin-3.
Although the interest in the physiological role of endothelin-3 is increased as described above, basic physiological information such as the expression site or plasma level of endothelin-3 has scarcely been obtained until now. This is mainly caused by that any monoclonal antibodies specifically recognizing endothelin-3 or the precursor of endothelin-3 have hitherto not been prepared and that any immunoassays for specifically, high sensitively assaying endothelin-3 or the precursor of endothelin-3 have not been developed. These immunological procedures are considered to be one of the most effective means to study endothelin-3, particularly its metabolic pathways, secretory mechanism, receptor system, relation to the pathology and the like as a whole. The establishment of these procedures has therefore been earnestly desired in various fields.